The present invention concerns an elevating platform system for attachment to a vehicle, having a platform and a substantially parallel lifting mechanism which includes two horizontally separated carrier arms for supporting the platform, a parallel cylinder for pivoting the platform from its vertical traveling position into its horizontal working position and vice versa as well as a lifting cylinder for raising and lowering the platform in its working location, wherein the lifting cylinder engages a lifting cylinder lever which is borne for rotation about a pivot axis of the support arm and forms a force triangle together therewith, wherein a first support arm is elastically coupled in the stroke direction for motion together with the lifting cylinder lever and a second arm is connected to the lifting cylinder lever by means of a torsion profile.
An elevating platform system of this kind is e.g. disclosed in EPA 0980786.
EPA 0980786 discloses an elevating platform whose elevating lifting cylinder lever is horizontally displaced relative to the associated first support arm. The lifting cylinder lever and the first carrier arm are borne for rotation, independent of each other, about a common rotational axis and are connected to each other at a radial separation with respect to the common rotational axis by means of a bolt so that a free end of the first support arm proximate the platform is elastically coupled to the lifting cylinder lever for resilient motion in the lifting direction. After raising the platform up to the height of the truck loading level, further activation of the lifting cylinder facilitates further lifting motion of the lifting cylinder lever which is transferred to the second lifting arm by means of the torsion pipe. In this fashion, a step and gap free transition from the platform to the truck loading surface can be achieved even if only the platform is loaded.
EP-A-0808747 also discloses an elevating platform system with which a first support arm is disposed between two parallel separated arms. The two arms form, together with the lifting cylinder, a force triangle and are borne for rotation about the axis of rotation of the two carrier arms. The first carrier arm is welded to both arms at a radial separation with respect to the rotational axis by means of a transverse support so that its free end facing the platform is elastically, resiliently coupled for motion together with the lifting drive in the lifting direction.
EP-A-1106431 discloses an elevating platform system with which a spring is supported on the arm forming a force triangle together with a lifting cylinder, the other end of the spring being supported on the platform. The spring, elastically, resiliently couples the platform to the lifting mechanism for motion in the lifting direction.
EP-A-1221399 discloses an elevating platform system having a parallel arm disposed horizontally next to the first support arm which is borne for rotation about a common rotational axis independent of the first support arm and whose other end is connected to the first support arm by means of a universal joint. The lifting cylinder engages the universal joint between the first support arm and the parallel arm. The first carrier arm is elastically, resiliently coupled for motion in the lifting direction to the lifting mechanism by means of a resilient element which is supported at one end on the first support arm and on the torsion pipe at its other end.
DE-C-10205669 discloses another elevating platform system with which the lifting cylinder engages the first support arm by means of an elastic compensation unit. The elastic compensation unit is borne for rotation on the first support arm in opposition to the action of a spring. Through further activation of the lifting cylinder and following lifting of the loading platform up to the height of the truck loading surface, the compensation unit is thereby further moved in opposition to the action of the spring. This motion is transferred to the second support arm by means of the torsion pipe.
In contrast thereto it is the purpose of the present invention to simplify an elevating platform system of the above mentioned kind.